fuel leak down

[85 Cutlass Brougham]

The fact that it takes a little cranking if it sits for a while is normal. It may be that your area uses a fuel that evaporates quicker than other areas and you just need to refill the float bowl. The EPA mandates a variety of fuel formulations depending on geographical area and some have a different latent heat of vaporization than others.

Moving on to the carb, I do not have experience with this particular carb. The situation you describe has nothing to do with the float level either. I would try setting the mixture screws using a vacuum gauge and setting the mixture for the highest idle vacuum. Being that it has the oddball reverse setup, it may be entirely normal for it to operate in this fashion. I would then adjust the timing and idle speed after setting the mixture screws. The timing will also affect the idle speed, just like the mixture, so it is important to set the final idle speed last. You may have to exchange timing and mixture for idle speed a few times along the way, but again this is normal. Holley did make other spread bore carbs over the years. I have a real oddball 650 double pumper that is a spread bore. It is not a modular carb like the 4150/4160 series, but rather has a removable top like a Carter AFB. It was a "new" style carb they sold during the 90's but have since discontinued.

 

[megaladon6]

the carb and car is tuned perfectly. (i'm a mechanic) the fuel leak down is alot worse than i've seen before. it feels like most of the main line has drained back to the tank. it's not a major problem but it is strange.

according to holley the screws should be the usual 3 or so turns off the lean cut. i'm at about 1/8-3/16 of a turn out from cutoff.

did not know about the other spread bores, interesting.

 

[wolfs1959]

if your car is tuned perfectly why does it make a difference were the idle mixture screws are set, as long as its perfect?

Joe

 

[wolfs1959]

If theres no leaks and the fuel is bleading off that fast the first thing i would check is the fuel pump. mech. or not it still should hold "pressure"(for lack of beter word) while the car is sitting more than 2 days. simple gravety would drain the float bowls and lines. also I dont know much about gbody cars but there should be a vent for the tank usually runs next to the filler neck of the fuel tank if this line is plugged it could cause a vacum on the system itself and cause the fuel to run back into the tank this is a long shot but possible.

just my guesses though
Joe

 

[pontiacgp]

pay particular attention to the use of the word SOME. yes, some as opposed to ALL

and for those SOME they were not making reference to the 4175 carb..

but anyway your THE mechanic so please carry on...

 

[megaladon6]

pontiacgcp: you need to pay more attention

AGAIN!
read your link again, i'm getting tired of this. in regards to the reverse idle adjustment: "It is also in most 4165 ,4175 and in the emission/performance 4150 double-pumpers." see how it says most? if you are going to use a link, please read the WHOLE article.

if your car is tuned perfectly why does it make a difference were the idle mixture screws are set, as long as its perfect?

it's not a big deal but i like having some room to play with, especially on carb adjustments. as quite a few people have noted, holley's are very weather sensative. if i need to lean it out more i'm screwed.

pontiacgcp: i'm not THE mechanic, i'm A mechanic. two things every mechanic learns is that they don't know everything, and you need to ask questions. write that down.

 

[jae]

I agree with wolf, I'd check the fuel pump. It should hold fuel for a while, a couple days I would think. Now if you're talking about a week or more, then it's a gamble that it'll hold its pressure and have enough for the start-up and continued running. Have you tried a different pump?

Some cars need that extra pedal pump or two in order to start if it sits, even if it's one day. My '66 Impala would fire right up as long as it was sat for no more than a day. Any time longer I had to pump the accelerator a couple times to start. My '81 Calais could sit a week and would fire right up.

And you have run the basic check of pulling the the fuel line from the carb, have a hose run from it to a catch can, crank it to verify immediate fuel flow? :?: Can you see the squirters from the top of the carb (not that familiar with this carb)? If you can, have someone mash the accelrator to verify if fuel is flowing. Not doubting your knowledge but sometimes the simplest things are forgotten.

Good luck.

 

[megaladon6]

i did forget about the volume test, thanks. i do know that after it sits and i pump the pedal it does spray fuel. the engine will fire but not run. i have to crank it for 10-20sec then it will start and run. if i don't pump the gas it takes the same amount of time to catch. i have a clear filter before the carb and this is dry.

 

[85 Cutlass Brougham]

The EFI 95 Sentra I used to have ( before that dumb b*tch in the Rav 4 killed it!) had a similar condition after it sat for two days. It would not start unless you primed the whole fuel system by turning the ignition on but not cranking it then back to off wait 5 sec, on again then start. It had no leaks and I just thought it was a quirk of the car and let it be. It usually got driven 800-1100 miles a week and so rarely ever sat unless I got bored with it and drove the truck for a day. Oddly, the truck, also a Nissan, could sit for a month or two and start on the first crank with no need for priming ( I had stopped driving it daily for 2 years and it sat around as a parts hauler and dump hauler before the accident). My Cutlass does the same thing after about 4 days of sitting and I need to crank it for a few seconds to prime the carb then it starts. So, I dunno. If it were doing this after shutting it down hot then trying to restart it within an hour, you could surmise it was percolation and that you may need a carb heat shield. GM did this on some of its cars using a metal plate sandwiched between 2 carb to manifold gaskets.

 

[pontiacgp]

pontiacgcp: i'm not THE mechanic, i'm A mechanic. two things every mechanic learns is that they don't know everything, and you need to ask questions. write that down.

well think of what your saying...to change the idle screws from a bleed air adjustment to gas flow adjustment they have to change design of the metering blocks so if you think they are going to have a carb that has two different metering blocks for the same carb number then holley has really gone out of their way to confuse people....[/code]